1. Field of the Invention
The present invention relates to an object display method and apparatus for displaying a list of a plurality of objects.
2. Description of the Related Art
In general, it becomes popular for personal computers to refer to various contents held in other apparatuses connected via a network, and to display a list of reference information such as representative images of these contents in a specific order. With this list display, a list of various contents such as still pictures, moving pictures, music pieces, documents, and the like are displayed. Such list display will be referred to as an object list display or contents list display hereinafter. When the user issues an instruction to reference information (to be referred to as content information hereinafter) corresponding to an entity of a content in the contents list, an apparatus of this type allows the user to browse, edit, delete, and so forth the entity of the corresponding content.
In the aforementioned system, since a plurality of users may refer to an identical content group from different apparatuses, various problems are posed. For example, upon displaying a list of contents available in a certain environment, the user cannot often access a content currently displayed in the list display in practice depending on the display update timing. For example, assume a distributed environment in which a storage apparatus that holds contents and a contents list display apparatus that makes a list display of contents are connected via a network. Also, assume that the contents list display apparatus makes the list display including contents held in the storage apparatus in such a distributed environment. Under such circumstances, when the storage apparatus is disconnected from the network, the contents list display on the contents list display apparatus is no longer updated, and the contents list display apparatus displays an error only after the user is about to use a content.
The aforementioned problem occurs not only in the distributed environment. For example, when the user can manipulate available contents by a plurality of methods, he or she inadvertently deletes an arbitrary content by another method during the contents list display, thus posing a similar problem.
In order to avoid the aforementioned problem, Japanese Patent Laid-Open No. 2005-216451 has proposed a method of displaying information indicating inaccessibility for a content, that the user attempted to access once but failed to access, in a list display. According to the method described in this patent reference, since information indicating inaccessibility is displayed together with content information in the contents list display, the user can recognize inaccessibility of a certain content once that content is determined to be inaccessible.
As the contents list display method, a method of sequentially reflecting manipulation events of contents to the display is normally used. In this case, every time a manipulation event of a content occurs, the contents list display is updated. According to this method, since the conditions of contents can be recognized sequentially, accessible contents can be displayed at any time. For example, in the Explorer which runs on Windows® available from Microsoft Corporation, U.S.A., when another user deletes a shared file, that file ceases to display.
In general, in a list display which displays each content information using an icon or reduced-scale image (thumbnail), a certain content in which the user has an interest is expressed clearly by changing a display mode corresponding to that content in the list display. Note that a content in the contents list in which the user has an interest will be referred to as a content of interest hereinafter. As described above, in a system in which one content can be shared by a plurality of apparatuses, a certain user may delete a content of interest of another user. In order to avoid occurrence of such a situation, Japanese Patent Laid-Open No. 2005-071202 discloses a technique for displaying a content of interest of another user on the contents list.
However, even when the aforementioned technique is used, a phenomenon in which a content of interest in the contents list that a certain apparatus refers to becomes unreferable due to external causes or events cannot be avoided. The external events include manipulations such as deletion, movement, and the like of a content entity from another apparatus, disconnection of the network, power-OFF of an apparatus which holds that content, and the like.
As a method of updating the contents list upon occurrence of the phenomenon in which the content of interest becomes unreferable due to external events, a plurality of solutions have been proposed. For example, in Microsoft Windows®, content information corresponding to an unreferable content is deleted from the contents list, and the position where the deleted content information is turned to a vacant state. Also, the following method has been proposed. That is, when a content entity corresponding to a content of interest becomes unreferable, the display position of the content of interest disappears once, and when the user selects arbitrary content information, display of the content of interest is resumed.
In another example, after unreferable content information is deleted from the contents list, subsequent contents in the contents list move over in turn to the position where the deleted content information is allocated, thereby updating the display. In this case, in one method, when a content corresponding to content of interest becomes unreferable, content information which exists at a predetermined default position (e.g., a head position) is displayed as a new content of interest. In another method, the displayed position of the content of interest remains unmoved, and content information allocated at that position after updating the display is displayed as a new content of interest.
An addition/deletion of contents to be displayed on the list display is not limited to the above description. For example, upon acquiring contents that the user requires from those in large quantities, a technique for refining a search to retrieve contents that meet the use purposes and displaying retrieved contents is needed. To meet such needs, Japanese Patent Laid-Open No. 2005-174256 has proposed a method of searching for contents based on attribute information of user's choice, and displaying the search result as a new list display. This method finds, at last, contents that the user wants by repeating selection of attribute information and the list display of the result.
As a method of displaying a new list after a search, subsequent contents in the contents list move over in turn to the positions where contents which are excluded from those to be displayed as a result of the search were allocated, thereby updating the display. In this case, in one method, when a content corresponding to a content of interest is excluded from that to be displayed, content information which exists at a predetermined default position (e.g., a head position) is displayed as a new content of interest. In another method, the displayed position of the content of interest remains unmoved, and content information allocated at that position after updating the display is displayed as a new content of interest.
With the method proposed by Japanese Patent Laid-Open No. 2005-216451, whether or not there are available contents cannot be determined unless the user makes an access at least once. With the method of updating the display every time an event for a content occurs, a user's manipulation on a certain screen is often disturbed since the display of that screen is updated during the manipulation. Also, with the method of updating the display every time an event for a content occurs, when an add event of contents occurs, added contents spread across the screen, and the user may hardly manipulate on a large screen.
Furthermore, the aforementioned conventional contents list updating method suffers the following problems. In an apparatus having no pointing device such as a mouse, digitizer, or the like, if a content of interest is absent, it becomes difficult to select a content to be browsed or manipulated. Upon updating the contents list, when the position of a content of interest on the display has been changed, and particularly when the contents list has been updated due to an external event, the position of interest on the display suffers a change that the user did not intend, resulting in confusion. Upon keeping the position of a content of interest on the display, content information which happens to be allocated at that position after the display update is to be handled as a content of interest. For this reason, for example, when the user refers to contents in the order of the list, the content of interest in the contents list may largely deviate, and the user loses how far he or she has browsed, also resulting in confusion.
Furthermore, with the method proposed by Japanese Patent Laid-Open No. 2005-174256, the display is updated every time a contents search or refinement is conducted. In this way, a user's manipulation is often disturbed since the display of the screen on which he or she is manipulating is updated. More specifically, when the user loses a content of interest upon updating the list display, he or she needs to search for that content of interest. For this reason, when the user makes manipulations for contents in turn while refining contents, if the content of interest has changed, he or she cannot smoothly continue manipulations.